SPIN

The spin and charge Nernst effects in a four-terminal ferromagnetic graphene are theoretically investigated by using the nonequilibrium Green’s function method. The results of this study reveal that (1) when the four leads are normal graphene, the pure charge Nernst effect can be obtained under the assistance of magnetic field, (2) when the ferromagnetic graphene leads are in a parallel configuration of the magnetizations, both the spin and charge Nernst effects can be generated simultaneously, it is worth noting that, for the first two cases, the Nernst effect cannot be obtained without the $z$ direction magnetic field, and (3) the pure spin Nernst effect (without charge Nernst effect) emerged only by the temperature difference for the antiparallel configuration. In addition, the magnitude of the spin and charge Nernst coefficients can be tuned by adjusting the strength of magnetic flux and exchange field. All the results indicate that the proposed multi-terminal graphene nanosystem is a promising candidate for spin caloritronics devices.

In this paper, we investigated the conductance properties in the helimagnet (HM)- and skyrmion lattice (SL)-film-embedded electron waveguide (WG) and found that under translation of the HM/SL layer the conductance contour as a function of the layer center demonstrates nearly identical pattern to the original spin field contour. When a WG electron is scattered by the embedded impurity, the HM/SL spin texture distorts the spin-dependent wavefunction. By interference between different quantum paths the electron experiences, the HM/SL spin texture is recorded in the conductance. The scheme also provides a possible detect of the HM/SL spin configuration by transport experiment.

Schrödingerand Poisson equations are solved self-consistently in order to obtain the potential and charge density distribution in $n$-type GaN nanowalls tapered along $c$-axis by different angles. The study shows two-dimensional (2D) quantum confinement of electrons in the central vertical plane of the wall for the entire range of tapering. Calculation of room temperature electron mobility in the 2D channel shows a steady decrease with the increase of the inclination angle of the side facets with respect to the base. However, it is interesting to note that the mobility remains to be much larger than that of bulk GaN even for the inclination angle of 65${}^{\circ }$. The properties of high mobility and the vertical orientation of the 2DEG plane in this system can be exploited in fabricating highly conducting transparent interconnects and field effect transistors, which can lead to large scale integration of 2D devices in future.

We demonstrate an electric field control of spin lifetime at room temperature, across a semiconducting interface of Nb:STO using Ni/AlO_x as spin injection contacts. We achieve this by a careful tailoring of the potential landscape in Nb:STO, driven by the strong response of the intrinsically large dielectric permittivity in STO to electric fields. The built-in electric field at the Schottky interface with Nb:STO tunes the intrinsic Rashba spin–orbit fields leading to a bias dependence of the spin lifetime in Nb:STO. Such an electric field driven modulation of spin accumulation has not been reported earlier using conventional semiconductors. This not only underpins the necessity of a careful design of the spin injection contacts but also establishes the importance of Nb:STO as a rich platform for exploring spin–orbit driven phenomena in complex oxide based spintronic devices.

In the present work, Al${}^{3+}$ substituted cobalt ferrites (CoFe${}_{2-x}$Al_xO₄, $x=0.2$, 0.4, 0.6, 0.8) have been synthesized via standard solid-state reaction technique. The incorporation of Al${}^{3+}$ ions in cobalt ferrite has been shown to play an important role in modifying the magnetic properties. The room temperature (300K) ${}^{57}$Fe Mössbauer spectra reveals that the studied samples show two characteristic ferromagnetic zeeman sextets at A and B-sites at lower Al${}^{3+}$ ion concentration (i.e., up to $x=0.4$). However, a paramagnetic relaxation has been noted for higher Al${}^{3+}$ substitution (for $x=0.6$ and 0.8) samples. The dependence of the Mössbauer parameters such as isomer shift, quadrupole splitting, line width and magnetic hyperfine field on Al${}^{3+}$ ion concentration has also been noted. The variations in initial permeability over a wide frequency range (125kHz to 30MHz) at 300K have been recorded. The fairly constant values of initial permeability and the low values of the relative loss factor of the order of 10${}^{-4}$ to 10${}^{-5}$ over the wide frequency range are the important findings of the present work. The observed low values of relative loss factor at high frequencies suggest that the studied ferrites are promising materials to be used in microwave applications.

In this paper, with the three-band tight-binding model and non-equilibrium Green’s function technique, we investigate spin transport in electric-barrier-modulated Ferromagnetic/Normal/Ferromagnetic (F/N/F) monolayer (ML) zigzag MoS₂ nanoribbon junction. The results demonstrate that once the double electric barriers structure emerges, the oscillations of spin conductances become violent, especially for spin-down conductance, the numbers of resonant peaks increase obviously, thus we can obtain $100\%$ spin polarization in the low energy region. It is also found that with the intensity of the exchange field enhancement, the resonant peaks of spin-up and spin-down conductances move in the opposite direction in a certain energy region. As a consequence, the spin-down conductance can be filtered out completely. The findings here indicate that the present structure may be considered as a good candidate for spin filter.

Using the Floquet theory and effective-mass approximation theory, we have investigated the terahertz (THz) photon-assisted transport through a magnetic-field tunable diluted magnetic semiconductor (DMS) structure with a nonmagnetic barrier under multi-physical fields, including an external magnetic field, an electric field and a THz field. It is found that a THz field and an electric field can greatly affect the transmission coefficient and current density as well as the corresponding polarizations. As a result, some asymmetric ‘Fano’ type transmission resonance appear at some specific energy. With the applied bias increasing, some quasi platforms of the polarization began to take shape. Furthermore, the transmission coefficient suppression or augmentation can be clearly seen from the variation tendency of current density. It is noteworthy that the amplitude of current–density polarization becomes larger under a THz field and a small magnetic field. These remarkable properties of spin polarization might be beneficial to the design of spin filtering devices.